A vehicle air conditioner described in JP-A-9-263121 includes first and second heat exchangers and a heater, which are accommodated in one air-conditioning casing. The first heat exchanger and the second heat exchanger perform heat-exchange between refrigerant circulating in a vapor compression refrigerator and air to be blown toward a passenger compartment. On the other hand, the heater heats the blown air using engine-cooling water as a heat source. However, in this vehicle air conditioner, the two heat exchangers and the heater are accommodated in the heater casing. Thus, the mounting performance of the air conditioner is deteriorated, due to its large size.
In a vehicle air conditioner described in JP-A-11-115466, a sub-condenser of a refrigerant cycle and a heater are disposed in an air-conditioning case serially in an air flow direction. The sub-condenser is for heat-exchanging between high-pressure refrigerant discharged from a compressor and air blown toward a passenger compartment. The heater heats the blown air using engine-cooling water as a heat source. However, because the sub-condenser and the heater are disposed serially in the air flow direction, pressure loss is increased while air passes through the sub-conditioner and the heater.